The present paper aims to proceed to a succinct analysis of Leibniz’s Principles of Nature and Grace (section 5), by exploiting the cardinal arguments acquainted in it – namely, is he human distinguishable from the animal thanks to his capacity of being endowed with rationality? Henceforth, for answering this question, the herewith paper obeys to a linear analysis and presents a corpus structured in three main parts. The first two parts aims to highlight the text, through furnishing explanations on the main concepts and concerns, while the third part of the corpus offers at prima facie a criticism towards the Leibnizian principle – according to which humans are rational – in order to finally strengthen this latter principle, by emphazing that there are no solid disparagements (confutatio) towards it.